By a series of micromanipulative and microinjection procedures, we propose to continue investigations of the role of small nuclear RNA's and nuclear proteins in cell function--particularly in the regulation of transcriptive activity and the organization of chromatin in amebas. With cultured mammalian cells, we propose to investigate the relation of snRNA composition to different states of chromatin before and after Friend's erythroleukemia cells have been induced to differentiate in vitro. We also will investigate whether changes in snRNA can be correlated with differences in cellular content of constitutive heterochromatin (or satellite DNA). Finally, we will investigate by cytological means whether nuclear actin has unique intracellular localization and behavior.